Well drilling operations generally comprise the steps of connecting drill pipes to form a drill string and rotating the drill string to turn a drill bit thereby abrading the earth formation. In other cases, non-rotating coiled tubing with an electrically or hydraulically operated drill may be used. In any case, during drilling operations, operators must measure various drilling parameters such as drilling formation, inclination, temperature, PH and the like. Instantaneously sensing, measuring, transmitting, and detecting such parameters has been a problem, in part because the drill string rotates and the parameter being measured is often thousands of feet below the earth's surface.
Commonly, drilling mud is pumped downwardly through the drill pipe to cool, lubricate, and flush cuttings from the drill bit. The mud is then returned to the surface in the annulus around the drill string. The cuttings entrained in the return mud may then be analyzed to determine the type of formation that the drill bit is encountering at that time. Drilling operations may then be altered to more efficiently drill through that type of formation.
It has been recognized in the art that providing multiple channels for conducting drilling mud to the drill bit and to the surface can enhance the effectiveness of returning drill cuttings to the surface. One structure for accomplishing this includes a dual passage drill pipe including inner and outer concentric pipes.
For example, the most efficient drilling operation occurs when the characteristics of the formation are known to the drilling operator. For different types of formations, such as rock, soil, shale, sandstone, or other types, it may be desirable to alter the surface operations to effectively deal with the type of formation in which the drill bit is presently encountering. Traditionally, the formation chips eroded by the drill bit are carried uphole in the annulus around the drill string by fluids pumped downwardly through the drill pipe. The inspection of these chips, however, provides only unreliable information of formation presently being drilled, as it may take a substantial period of time for the chips the ascend to the surface. Non-concentric, multi-conduit drill pipe may also be used to increase the number of conduits. Such pipes have not found widespread application for a number of reasons. One drawback encountered in connecting such pipes together is the manner in which the conduits of one pipe are sealed to the conduits of another pipe. Conventional sealing arrangements can limit the pressure of operating of such a system.
Further, there is a need to monitor downhole drilling parameters, instantaneously transmit the parameters to the surface, commonly by an electrical conductor. The conductor must be combined with the drill pipe in such a way that the drilling mud carrying capability is not compromised. One structure that has been proposed to accomplish this uses the central bore of the drill pipe as a chamber in which an electrical conductor is run. However, the conductor insulation is subjected to the aggressive nature of drill fluid, or expensive shielding must be used.
Another problem with the use of electrical conductors in the fluid-carrying bore is the isolation of the connections of lengths of conductor from the drilling fluids. This problem is exacerbated because the drill pipe is rotating, and none of the proposed solutions has proved entirely satisfactory.
Even after the drilling operation has been completed, there is a need to monitor downhole parameters during the production phase for well management purposes. Conventional well casings have heretofore afforded a high degree of integrity to the well bore, but are ill-equipped to provide passageways for wires, gasses or liquids other than the fluid pumped upwards. As a stopgap measure, telemetry wires have been secured to the outer periphery of the casing by metal or plastic bands and extended downhole to telemetry equipment. It is also well known to provide parasitic pipes external to the casing for carrying air pressure to create artificial lift downhole.
Casings have been lined previously, as shown in Vloedman, U.S. Pat. No. 5,454,419. In this case, the lining provides corrosion protection and is used to patch the primary casing. The system may also be used for production conduit, but makes no allowances for channels between the lining and a host tubular.
Curlett, in U.S. Pat. No. 4,683,944 proposed a solution to the need for multiple conduit drilling pipe. Curlett teaches a plurality of conduits distributed uniformly throughout the drill pipe and thus uniformly across tool joints. The conduits extend axially through the drill pipe, from one of the drill pipe to the other. Such a structure shows promise in solving the problems in the art just described, but suffers from two drawbacks, in that the manufacture of the drill pipe is far more expensive than drill pipe without the multiple conduits, and the ultimate torsion strength of the drill pipe or the same wall thickness is lessened.
As a result, there is a need for multi-conduit well tubular and/or casing through which the production fluid can be pumped, as well as a plurality of additional conduits for housing telemetry wires and other uses, which drill pipe does not add significantly to manufacturing costs and which retains the torsional strength of the drill pipe of a predetermined wall thickness.
Pipe and other tubulars have been lined with polymeric liners (e.g., polyethylene, nylon 11, etc.) for many years and several installation techniques are known to the art. These systems have been used principally in offshore and onshore pipelines, and in downhole production tubulars. The application of such liners has generally been limited to corrosion and erosion protection. However, they have also been used in monitoring for integrity of the composite liner-host system, as shown by Roach and Whitehead in U.S. Pat. No. 5,072,622, incorporated herein by reference.
Roach and Whitehead taught a lined pipe with it least one groove located in the exterior surface of the liner. The at least one groove was in communication with a leak detection system, and was maintained at a vacuum to detect leakage by variation in the vacuum. Further, all of the grooves in the liner were linked together with cross passages so that no one of the grooves was isolable from any other groove. Thus, the system of Roach and Whitehead was not adaptable to provide downhole channels for the conduction of fluids, or to provide channels for non-crushable members such as electrical conductors, tubulars, and the like.
In other known liner systems, the liner resides in close-tolerance with the host pipe along its length, forming a stable composite system. The installed liner may be either loose-fit or compressed-fit. In all but low pressure applications, the stresses induced by fluid pressure from within the liner are transmitted to the surrounding host tubular and the host tubular resists these transmitted stresses. The liner acts as an intermediary layer.
A variety of techniques for lining pipe are currently in use, but each generally involves temporarily reducing the outside diameter of the liner to less than the inside diameter of the host tubular, pulling the liner into the host tubular, then permitting the liner to expand into abutting contact with the inside surface of the host tubular.
However, if the liner configuration could be modified from its usual uniform cylindrical shape, then a number of possibilities are presented, including the formation of multiple conduits between the liner and the host tubular. This structure thus suggests a relatively inexpensive technique for providing multiple conduits within a drill pipe, while retaining the torsion strength of the drilling pipe since the conduits do not go through the drill pipe itself.